The present invention relates to sheet-like compact electronic devices having a small thickness (e.g., 1 mm or less).
In the latest compact electronic devices such as an electronic calculator, a compact electronic watch and an electronic game machine, the thickness of the outer case tends to be decreased so as to improve portability.
In a portable/compact electronic calculator, for example, it is desired that the outer case be compact like a credit card and have a small thickness, and that the upper surface of the outer case be flat without any projection. In the compact electronic calculator of the type described above, a synthetic resin is conventionally used to mold an outer case which has component parts such as a wiring board, a display panel and a dry cell therein. Alternatively, the outer case is formed by a synthetic resin in combination with a metal plate.
However, the outer case must be thick enough and rigid enough to protect various component parts from an outside force. For these reasons, the thickness of the outer case cannot be smaller than 1.6 mm. As a result, the conventional compact electronic calculator cannot have a thickness of 1 mm or less, unlike the credit card. Furthermore, in most of the conventional electronic calculators or the like, a display unit and keys project from the upper surface of the outer case, thus resulting in inconvenience and degrading portability.